Process and apparatus for oxidizing combustible material



June s, 1933. A. o. JAEGER 1,913,054

PROCESS AND APPARATUS FOR OXIDIZING COMBUSTIBLE MATERIAL Filed June 22, 1931 Kane/nae INVENTOR ALFHUNS ELJAEZGEIR ATTORNEY Patented June 6, 1933 UNITED STATES PATENT OFFICE ALZPHONS 0. JAEGER, OE MOUNT LEBANON, PENNSYLVANIA, ASSIGNOB TO THE SELDEN COMPANY ,OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF DELAWARE A PROCESS AND APPARATUS FOE OXIDIZING COMBUSTIBLE MATERIAL Application filed June 22,

This invention relates to process and apparatus for oxidizing combustible materials to intermediate oxidation products, and more specifically to-certa'in embodiments in temperature control of such oxidations and preparation of the reaction mixtures.

In the past, the vapor phase air oxidation of such combustible materials as aliphatic and aromatic hydrocarbons, phenols, alcol0! hols, acids, esters and the like has been accompanied by many difficulties, both in control and maintenance of the temperature 0 the reaction and in the preparation of a suitable reaction gas mixture.' Ordinarily'such materials have been vaporized in the pres ence of air, either by passing an air stream through or over a liquid body of the material to be oxidized, maintained at suitably f elevated temperatures, or by spraying or otherwise diffusing the material in finely divided form into a stream of air or other oxygen containing gas. Reaction mixtures so produced are often explosive, particularly when hydrocarbons such as naphthalene, acenaphthene, benzene, toluene or crude or purified anthracene are vaporized, for the amount of oxygen required by the reaction is such that a vapor well within the explosive limit is obtained. Moreover, since the vaporization temperatures of many of these substances are I which shows diagrammatlcally two embod quite high, great care must be taken to keep the reaction mixture from contact with any substance which will act as an ignition catalyst, and such substances as iron rust, con- 3 verter scale, oreven the pyrolytic coke which tends to accumulate in the Vaporizers and become entrained in the gas stream are always a source of fire danger. The present invention provides a novel 40 process and apparatus for overcoming these and other difficulties by an arrangement which at the same time provides a complete control of the course of the reaction during catalysis. It has been found that the temperature of the catalyst in the converters can be properly maintained by means of a nonboiling bath surrounding the catalyst tubes, heat given off by the reaction being-transmitted through the bath to cooling elements 5 through which air or other gaseous media oxidation of naphthalene to phthalic an- 1931. Serial No. 546,066.

are passed, and in my prior application Serial No. 448,410, filed April 29,1930 the use of this cooling gas, suitably preheated by the bath, has been proposed for use in the vaporizers, which provides an excellent method of utilizing the heat given 'ofi' but does not in any way overcome the fire hazard.

According to the present invention, vaporization is efiected entirely by means of steam or other noncxidizing gases such as carbon dioxide, nitrogen, stack gases and the till f like without the addition of oxygen or with the use of only such small amounts of oxygen as will not create a fire hazard. The material vaporized in this manner is then mixed with air or other oxygen containing gas which has been preheated by heat exchange with the non-boiling bath just before the mixture is subjected to catalysis, thus avoiding the danger of explosions in the vaporizer or the passage of an explosive mixture through any length of piping which might become oxidized thereby and produce a pyrolyt ic oxide. The invention also provides for the suitable regulation of the amounts and temperature of the oxidizing air, in order to add flexibility to the process and enable its application to a wide range of materials.

The invention will be described in conjunction with the accompanying drawing ments thereof, and in which Fig. 1 represents a, systemsdesigned for intensely exothermic reactions, such as the hydride, in which more air is needed to cool the converter than would be required to effect a satisfactory oxidation of the reaction mixture; and

Fig. 2 shows a system wherein all the air necessary to control the bath temperature is used in forming the reaction mixture, this arrangement being suitable for'less strongly exothermic reactions, such as the oxidation of anthracene to anthraquinone, acenaphthene to naphthalic anhydride and toluol to benzaldehyde and benzoic acid.

Referring to Fig. 1 of the drawing, the converter consists. of a. shell 1, with top and bottom pieces 2 and 3, upper lower tube any other suitable purpose.

sheets 4 and 5, and spaced catalyst tubes 6 in which catalyst is retained by thelower screen 7. The tubes are surrounded by a. bath 8, which consists of material having a 5 boiling point above the reaction temperature,

such materials as lead, metal alloys such as mercury-lead or mercury-tin, or a eutectic mixture of sodium nitrate and sodium nitrite being suitable. Interspersed among the catalyst tubes and extending into the bath liquid are heat exchange tubes 9, adapted for the passage of air or other cooling gas in heat exchanging relation with the bath liquid. In the modification shown, these heat exchange elements are shown as telescoping, double countercurrent tubes, consisting of an inner, open end tube 10 and an outer, closed end tube 11. All the inner tubes 10 are connected together at their tops by means of a connecting manifold 12, which is in turn connected with inlet pipe 13 through which the cooling .gases'are admitted. In similar manner, the outer closed end tubes '11 are connected-at their tops by the manifold 14, a continuation of which serves to lead the hot gases away from the converter shell.

The material to be oxidized in the converter is fed through inlet pipe 15 into vaporizer temperatures by means of steam, CO or other inert gases such as those issuing from the converter, after removal of partial oxidation products therefrom, the absence of any large amounts of oxygen permitting the use of anydesired vaporizing temperatures without fire danger. Vapors from the vaporizer 16'are led to the converter through the pipe 17 in which there is also of course no danger of explosion. The air necessary for the vapor phase oxidation is taken from the outlet manifold 14 through the pipe 18, controlled by the valve 19, and is only admitted to contact with the vapors to be oxidized at the point 20 where the vapors are entering the converter and are subject to its temperature regulation. Excess air in the manifold 14 may be led through the tubes of a steam boilor as shown, where it serves to generate steam forthe vaporizer 16, or may be applied to The above described system permits'a close and exact regulation of the composition of thereaction mixture, for there is always an excess of preheated air ready for use and the vaporization is much more easily 'efiected with steam or other inert gases since much higher temperatures can be usedwith safety. t In the modification of Fig. 2 a converter is shown which is similar inconstruction to that of Fig. 1; but means for a defined recirculation of the bath material are provided. These means consist of a vertical baffle 31 which is placed aroundthe catalyst tubes 6 in order to provide, together with the converter shell 1, a cooling zone The heat 16, where it is vaporized at suitably elevated exchange tubes 9 are placed in this cooling zone instead of being interspersed among the catalyst tubes, and the bath liquid is caused to travel through the zone and downwardly along the catalyst tubes in order to efi'ect a more efiicient heat exchange with the gas passing upwardly within them. For small converters a simple thermosiphon flow such as that indicated .will be suflicient, but for larger installations it is advisable to provide a. central well together with impelling means such as a propeller for positive recirculation of the bath liquid.

The air or gases of higher or lower oxygen content which is used for cooling the bath enters through the manifold 33 and is passed downwardly through the inner tubes of the double countercurrent heat exchange elements 9 into the lower portions of the outer tubes 10, where it passes upwardly in countercurrent to the downward flow of bath liquid outside the tubes and becomes heated thereby. The mixture of steam and vapors to be oxidized is admitted at 34 and is deflected by the baflle 35, thus bringing it into intimate admixture with the stream of heated air coming from the heat exchange tubes 10, thecnds of which extend somewhat above the upper tube sheet 4 in orderto produce a more intimate admixture. Additional air is admittted through the valve 36 if needed, thus. adding flexibility to the system and permittinga close and exact regulation of the amount of air in the reaction mixture as well as providing an important means of cooling the reaction if for any reason an undue temperature rise is encountered. The mixture is then passed downwardly through the catalyst in the tubes 6, the product of the reaction leaving the converter, through the outlet 37.

The modification of Fig.2 provides a greatly simplified construction for only a single realized, for by introducing the oxidizing air either during entry of the vaporized material into the converterthere is no fire danger and the entire amount of heat necessary to bring the vapors to reaction temperature is supplied by the exotherm of the catalytic reaction itself.

What is claimed as new is:

. 51. A process of-oxidizing combustible materials, which comprises vaporizing the material with a gas containing insufiicient oxygen to-support combustion and adding an oxidizing gas to the vapors so formed just prior to contact with a catalyst.

2. A process of oxidizing combustible ma: terials to intermediate oxidation products, which comprises maintaining an oxidation an oxygen-containing gas,

liquid through cooling zones, vaporizing the material with a gas containing insuflicient oxygen to support combustion, passing an oxygen-containing gas in heat exchanging relation with the bath liquid in said cooling zones, and bringing it into admixture with the vapors just prior to contact of the latter with the catalyst.

4. Catalytic apparatus comprising a converter having vertical, catalyst-containing tubes, a bath liquid in said converter and surrounding said tubes, heat exchange elements in said bath liquid for the passage of a vaporizer, means for admitting a non-oxidizing gas porizer, an inlet connecting said vaporizer to said converter, and means for admixing oxidizing gas from the heat exchangers with the vapors from the vaporizer just prior to entry of the latter into the catalyst tubes.

5. Catalytic apparatus comprising a converter having catalyst-containing tubes, a bath liquid surrounding said tubes, heat exchange elements in contact with said bath liquid, means for admitting an-oxidizing gas to said heat exchange elements, means for leading away the oxidizing gas from said heat exchange elements, a vaporizer, means for admitting a non-oxidizing gas to said vaporizer, an intake pipe connecting said vaporizer with said converter, and means for admitting oxidizing gases into said intake pipe from the outlet of the heat exchanger. 6. Catalytic apparatus comprising a con verter having catalyst-containing tubes, a-

bath liquid surrounding said tubes, heat exchange elements in contact with said bath liquid, means for admitting an oxidizing gas to,

. said heat exchange elements, a vaporizer,

means for admitting a non-oxidizing gas to said vaporizer, porizer with the inlet of the converter and means permitting. ,the gas leaving the heat exchange elements to mingle with the incoming gases from the vaporizer.

Catalytic apparatus comprising a converter having catalyst-containing tubes, .a bath liquid surrounding said tubes, heat exchange elements in contact with the bath liq uid, said heatexchange elements including to said vameans connecting the vatubes closed at their lower ends, means for admitting an oxidizing gas to the inner tubes of said heat exchange elements, a vaporizer connected to the inlet of said converter, means for admitting a non-oxidizing gas to' said vaporizer, and means for bringing the gas from the outer tubes of said heat exchange elements into admixture with the vaporizer gas just prior to entry of the latter into the catalyst tubes. p

8. Catalytic apparatus comprising a con verter having catalyst-containing tubes set into an upper tube sheet, a bath liquid surrounding said tubes, heat exchange elements set into said upper tube sheet and in contact with the bath liquid, said heat exchange elements including inner, open-end tubes surrounded by outer tubes closed at their lower ends only and having their upper ends extending above said tube sheet, means for admitting an oxidizing gas to the inner tubes of said heat exchange elements, a vaporizer, means for admitting a non-oxidizing gas to said vaporizer, and a connection between said vaporizer and-the inlet of said converter, a catalytic apparatus comprising a converter having catalyst containing compartments, a bath liquid surrounding said catalyst compartments, heat exchange elements in heat exchanging relation with said bath liquid, means for passing an oxygen containing gas through said heat exchange elements, a steam generator, connecting means for causing-at least a portion of the gases exiting from the heat exchange elements to pass through the steam generator, connection from steam space of the steam generator to a vaporizer for combustible material, said vaporizer per-, mitting direct contact of the steam with the combustible materials, an inlet header to the catalyst compartments, connection from the vapor to said inlet header, and adjustable means for causing a portion of the oxidizing gas passing from the heat exchange elements to the vapor generator, to pass into the inlet header for the catalyst compartments.

Signed at Pittsburgh, Pennsylvania, this 18th day of June 1931.

ALPHONS O. JAEGER.

inner, open end tubes surrounded by outer 

